Metalworking conditions promote corrosion of the metal surfaces involved. This is particularly relevant for ferrous metal, but not restricted thereto, e.g., copper may suffer from serious corrosion damage upon metalworking without adequate corrosion protection. Therefore, metalworking fluids usually contain corrosion inhibitors to protect the metal surfaces from corrosion. Metalworking fluids for machining ferrous and non-ferrous metals such as copper or aluminum and their alloys are generally water-based soluble oils that, upon dispersion in water, form transparent, translucent, semi-translucent, or milky emulsions. The oil employed is usually mineral oil-based and often contains such additives as natural fatty oils, synthetic esters or naturally sourced fatty acids, e.g., those that are biodegradeable. Said emulsions are susceptible to biological attack and are therefore generally treated with anti-microbial additives (biocides). Mineral oil-containing water miscible products generally contain emulsifier additives and hence can suffer from biological attack. They may have poor longevity because the emulsified phase containing the mineral oil tends to separate out.
Metalworking fluids often make use of amine borate containing corrosion inhibitors. Amine borate containing corrosion inhibitors are known to provide very good corrosion inhibition and, in addition, have biocidal activity. Such activity is in principle desirable as metalworking fluids contain contain water and oil—and thus, are prone to biological growth. Microbiological contamination within a metalworking fluid has detrimental effect on the life of the fluid, as it degrades certain components of the fluid, such as sodium petroleum sulphonates. The use of amine borate corrosion inhibitors therefore reduces the biocide requirements for the metalworking fluid.
However, amine borates are known to have a negative environmental impact, cause health hazards, and are generally undesirable in industrial applications. Consequently, there is a need for the reduction or elimination of the use of amine borates. In the past, several amine corrosion inhibitors have been suggested to replace amine borates. Among these amines, dicyclohexylamine, 3-amino-4-octanol, monoethanolamine and triethanolamine have seen commercial application. However, corrosion inhibition using these inhibitors is generally attributed merely to their basic nature. For example, dicyclohexylamine faces a decline in acceptance due to it being a secondary amine, which, in the presence of nitrites, form nitrosamines which are known to be toxic. In addition, corrosion inhibition provided by these amine subsitutes generally does not compare to the performance shown by conventional amine borates. Thus, whereas there are a number of additives available that can provide some of the attributes of amine borates, there are no readily available alternatives that can be used in place of the amine borate derivatives to match all the attributes required, and at the same time meet future environmental and health safety standards.
To address this, a compound is needed that works as a boron-free corrosion inhibitor and provides corrosion inhibition, biostability, hard water tolerance, low foam, formulation stabilization, and/or lubricity.